It has long been known that meat may be treated with carbon monoxide to maintain a color in the meat product. In particular, carbon monoxide treatment may produce a bright red color in the meat product. U.S. Pat. No. 4,522,834 to Woodruff et al. discloses a process of treating meat products with carbon monoxide gas to modify the color at the surface of the meat product.
It has also been proposed to use carbon monoxide gas as a preservative in meat products. U.S. Pat. No. 6,270,829 to Shaklai discloses a process where raw meat is exposed to carbon monoxide gas for a sufficient period to saturate the meat with carbon monoxide to inhibit microbial activity in the meat product. The Shaklai patent also discloses that the carbon monoxide saturation in the meat product produces a color change throughout the meat product.
Carbon monoxide gas has also been used in an injection material to treat meat products. U.S. Pat. No. 3,119,696 to Williams discloses injecting meat with a water and gas combination for the purpose of improving the tenderness of the meat. The Williams patent discloses that the gas is included in the water/gas treatment material to help facilitate absorption of the water fraction into the meat. The Williams patent also discloses that carbon monoxide may be included in the gas portion of the water/gas combination in order to modify the color of the meat in the interior of the meat product.
The change in color from carbon monoxide treatment results from the reaction of carbon monoxide with hemoglobin and myoglobin in meat products to form carboxyhemoglobin and carboxymyoglobin respectively. The microbial activity inhibiting effect of carbon monoxide in meat products is at least in part produced by reducing the oxygen content in the meat product. This reduction in oxygen content creates an unsuitable environment for aerobic microbes. Carbon monoxide treatment may also inhibit the growth and propagation of anaerobic microbes as well.
Despite the benefits, there remain certain problems associated with treating meat products with carbon monoxide. One problem with treating uncooked meats with carbon monoxide is that the treatment may affect the color of the product after the meat begins to spoil and after cooking as well as before. In particular, prior art carbon monoxide treatments may leave the uncooked meat with a bright red color that remains in the meat even after it is cooked. This unnatural red color in the cooked meat product occurs throughout the product where the entire product is saturated with carbon monoxide. Even where only the surface of the meat product is saturated with carbon monoxide, the surface of the cooked meat product may have an unnatural red color and the meat may not brown properly. Thus, although the carbon monoxide treated, uncooked meat product may have an appearance that is desirable to consumers, the color in the uncooked meat product may mask spoilage and the color remaining in the cooked meat product may be unacceptable to consumers.